AFM & DFM are fuel management systems used on modern GM vehicles to improve fuel economy. The systems works by shutting off, or deactivating, certain cylinders during specific driving situations. The technology is also referred to as Displacement on Demand, or DoD, which is a broader term to include both AFM and DFM, which are very different technologies when you get into the details.
These systems are said to improve fuel economy by 5%-7% but in reality cause a number of serious engine problems, like lifter failure, that can result in thousands of dollars in repair bills.
In addition to creating issues like lifter failure and excessive oil consumption it also has a number of unintended consequences like rough shifts, delays and hesitations while accelerating, and overall creates a less-smooth driving experience. All caused by the constant shifting back and forth between V4 and V8 modes, or in the case of DFM, shifting between 17 different modes.
Ultimately, for both performance and reliability reasons the best way to address active and dynamic fuel management is by disabling the system, or completely deleting it.
How to Get Rid of AFM & DFM
When it comes to turning GM's fuel management technology off there are really two main options:
- Disabling the system, or
- Completely deleting it
What's the difference? There is basically two things at a high level that make displacement on demand work: software and hardware. In addition to software, engines with AFM or DFM also use very specialized hardware, most notably a different style of lifter that is required for each specific cylinder to actually be able to be shut off. The main problem with active fuel management is lifter failure - and this is in part because of the specialized lifters and how they are designed.
Disabling AFM and DFM just shuts the software off so that it never engages, therefore keeping your vehicle in V6 or V8 mode 100% of the time. It is a simple solution but the downside is you still have all the hardware in your engine.
Deleting it is the process of actually swapping out all of the hardware that makes displacement on demand work, and then turning the software off via programing.
Which is Better?
Deleting AFM or DFM is going to be the only way to 100% guarantee that you don't experience lifter failure or any of the other problems with these technologies. But there is a lot of hardware that therefore needs to be removed. You'll need new lifters and a new camshaft among a number of other things, and ultimately, these parts are expensive and difficult to replace which makes the route of deleting these systems cost thousands of dollars in parts and labor.
Ultimately the cost of fully deleting AFM and DFM makes disabling the software a way better route. It is cheaper, easier to do, and completely reversible. While it doesn't provide 100% protection it drastically decreases the chances of having a failure and also removes all the annoying rough shifts and acceleration issues.
But, we'll teach you how to do both anyways.
How to Disable Displacement on Demand
Fortunately, disabling active and dynamic fuel management is extremely easy for most vehicles. All you need is a plug-and-play disabler device, like our Boost AFM & DFM Disabler.
The device simply plugs into the OBDII port and basically sends a message to the engine telling it to always stay in V6 or V8 mode. It does this without reprogramming your ECM which means it is completely undetectable to a dealership for those of you that still have warranty. Simply unplug the device and the engine will return to normal as if it were never there.
Disabling via Tuning/Flashing
A disabler device is the easiest option, but if you are already tuned or plan on doing some performance modifications then turning the software off via tuning is an easy option.
This route will require you to have a handheld tuning device, or to have your vehicle live tuned, and is generally going to cost around $500 or more but the benefit is you also get some performance benefits from it. This route will reflash your ECM which will void any warranty if you do have any.
Flashing is the Only Option for Newer Models & 10-Speed Transmission
Newer GM vehicles will have the DFM technology and most of them have already switched to GM's new 10-speed transmission. The TCM & ECM communicate differently on engines with these transmissions and therefore a simple disabler device, like our Boost device, isn't available yet on the 10-speed vehicles.
The 10-speed vehicles are now standard in Silverado and Sierra's since the mid-year 2022 refresh meaning tuning is the only option for these newer vehicles. Same goes for Tahoes, Suburbans, etc. from 2020 onwards.
The downside is that flashing it out requires you to remove your ECM and send it in to be unlocked - then you need tuning software and hardware and ultimately ends up costing $1,500-$2,000 and voids any factory warranty.
How to Delete AFM
There are a lot of components that are specific to these engines with displacement on demand. To fully delete the system you have to replace all of the hardware. It is definitely worthwhile to delete it all if your lifters have already failed and you have to have the labor done to replace them anyways. But otherwise, it is rather expensive parts and labor wise.
Here is a list of everything required to delete AFM or DFM:
- Camshaft
- Lifters
- Valley Cover
- Oil Pan Pressure Relief Valve
- Oil Pump
And then you will need to tune out all the check engine lights this will cause with a tuner.
Cost
A high quality delete kit can be bought for $1,000 or so which isn't terrible at all. However, quotes from a shop will typically be around 25 hours or so of labor which usually comes out to around $3,000 in labor. Ultimately, a full delete will cost somewhere in the ballpark of $4,000 and then you will need to spend another $500 or so on tuning.
To Delete or Disable...
Deleting is the best option for total protection - but running into an issue with a failed lifter is ultimately going to cost around the same amount as deleting it all. So it generally makes the most sense to do it if your lifters have already failed and you're doing all the labor to replace them anyways.
Otherwise, the best option is going to be to disable it for a fraction of the cost. If you are doing a high performance build and planning a new camshaft anyways, custom tuning, and all of that then there are some benefits to doing it upfront but otherwise disabling it will provide the most protection for the price.
